The present invention relates to communication between a print server and print clients on a computer network.
In a known print server system 1 (See FIG. 1) a print server 3 acts as an intermediary between clients 2 and one more printers 8 in arranging for print jobs generated on the clients 2 to be printed on the printers. The server 3 provides functions such as queuing of jobs and logging of the amounts of printing done.
In this known system the client 2 communicates with the print server 3 by means of an open HTTP request 4, i.e. one in which the server does not immediately send a response leaving the possibility of a later response. (HTTP stands for the “Hypertext Transfer Protocol”.) This means that each client keeps a respective HTTP request to the server open and waits for information 5 to be transmitted back to it from the server 3 via this open HTTP request, i.e. as the HTTP response. The information 5 transmitted back to the client may be, for example, about some event, such as the completion of a print job, and so on. The information may be in the form of an HTML page which is displayed to the user as a popup window. An example of that would be a job ticket for a print job with input fields for print settings (e.g. stapling, duplex printing etc.); when the user the user has completed those the setting data is returned to the server in HTML format. The “UNIFLOW OM”® (trademark) print servers and clients are ones that use this form of HTTP communication.